Spread of infection and sequelae

Pus, once formed, may remain localized at the root apex with the formation of a chronic abscess which can develop into a focal osteomyelitis, or may spread by various routes as shown in Figure 6.2. Pus may spread through the cortical bone of the jaws into the superficial soft tissues or, more rarely, into the adjacent fascial spaces. Once in the soft tissues the pus may (1) localize as a soft tissue abscess, (2) spread through the overlying oral mucosa or skin producing a sinus linking the main abscess cavity with the mouth or skin, or (3) extend through the soft tissue to produce a cellulitis. When dentoalveolar infection spreads deeply into soft tissues it tends to follow the path of least resistance, i.e. through connective tissue and along fascial planes. Extension of infection into deep fascial spaces is determined by the relation of the original abscess to the anatomy of the adjacent tissues. Students interested in the topic should consult a textbook on oral surgery. Infection via fascial planes often spreads rapidly and for some distance from the original abscess site and occasionally may cause severe respiratory distress, due to occlusion of the airway by oedema. Finally, pus may spread into the deeper medullary spaces of alveolar bone, producing a spreading osteomyelitis.

Clinical presentation

The presenting features of acute dental alveolar abscesses are very variable depending on (1) the site of infection, (2) the degree and mode of spread, (3) the virulence of the causative microorganisms, and (4) the efficiency of the host defence mechanisms. Usually a mixture of some or all of the following features are present: a non-viable tooth with or without a carious lesion; a large restoration; evidence of trauma; swelling; pain; redness; trismus; local lymph node enlargement; sinus formation; raised temperature and malaise due to toxaemia. A photograph of a typical dentoalveolar abscess is shown in Figure 6.3.

Microorganisms involved

A microbiological investigation on a non-contaminated sample of pus from a dentoalveolar infection may yield a single isolate, a mixture of two to three different bacterial species, or a complex mixture of microorganisms involving perhaps eight different species. A single isolate is unusual and a mixture of 3–4 different species much more common. Many earlier reports dealing with the microbiology of dentoalveolar abscesses have undoubtedly underestimated the incidence of strictly anaerobic bacteria, probably due to a combination of inadequate sampling and transportion to the laboratory, together with poor laboratory technique. Well-controlled studies have shown that strict anaerobes are usually the predominant organisms and that ’Streptococcus viridans’ is less common than one would assume from many reports. While almost every member of the oral flora has been isolated from dentoalveolar infection at one time or another, there is little doubt that some bacterial species are more common than others. The common species isolated from non-specific abscesses are shown in Table 6.1 and it is clear that strict anaerobes predominate (especially Bacteroides spp. and anaerobic streptococci), although facultative bacteria, e.g. Strep. milleri, are also found both in pure and mixed culture.

There is little information concerning the in vivo pathogenic potential of the bacteria commonly isolated from dental abscesses and therefore, until proven otherwise, all isolates should be regarded as equally important. Of course this is unlikely to be true, and there is good evidence that some strictly anaerobic bacteria, especially B. gingivalis, B. endodontalis and Fusobacterium spp. are more likely to cause severe infection than other bacterial species. There are a number of examples in medical microbiology where mixtures of strict anaerobes and aerobic or facultative bacteria are more pathogenic then either species alone. Such synergistic microbial interactions are likely to be important in the severity of dentoalveolar abscesses.

Collection and transportation of samples

The ideal sample of pus for microbiological assessment is a non-contaminated fluid sample which is transported directly to the microbiology laboratory. Details of the methods of sampling dentoalveolar infections and transporting the samples to the laboratory are described in Chapter 13